The present invention relates generally to a negative feedback amplifying circuit, and more particularly to a negative feedback amplifying circuit having a voltage negative feedback circuit and a current negative feedback circuit and performing an ideal for reactance load.
Generally, low-frequency amplifiers have negative feedback circuits to reduce the distortion of a signal and generation of noise. Especially, most of the low-frequency amplifiers which supply signals to speakers by amplifying audio signals have negative feedback circuits.
Therefore, majority of the speakers are generally determined of their sound quality by their driving voltage. Accordingly, when the load of the amplifier is a speaker, a voltage negative feedback amplifier is used as an amplifier so as not to cause unfavorable effect on the sound quality and the like.
However, voltage negative feedback amplifiers generally exhibit satisfactory performance when the load is of pure resistance, but when the load is a reactance load such as a speaker, the current distortion is not improved by the negative feedback. Furthermore, in the above case where the load is a reactance such as a speaker, low-frequency resonance due to mechanical impedance is unavoidably introduced at the speaker, and negative impedance in the vicinity of the minimum resonance frequency f.sub.0 of the above low-frequency resonance is increased, resulting in a drawback in that the sound pressure level decreased.